1. Field of the Invention
This invention relates generally to impact moving carriage printers and more particularly to means for printing in multiple colors in conjunction with a dot matrix print head.
2. Description of the Prior Art
Dot matrix impact moving carriage printers are well known and typically include a print head containing a plurality of solenoid actuated print wires to selectively drive each print wire against an inked ribbon located above the surface of a sheet or web of paper to print a row of dots to form an alpha-numeric character. The print head is conventionally mounted on a carriage which is adapted to move transversely across the paper while a predetermined number of print wires are selectively driven against the ribbon and paper to form a desired character or design. Illustrative examples of such apparatus include the printing systems disclosed in U.S. Pat. No. 3,941,051, entitled, Printer System", which issued to G. B. Barrus, et al. on Mar. 2, 1976 and U.S. Pat. No. 4,114,750, entitled, "Printer System Having Local Control Dynamically Alterable Printing", which issued to H. S. Baeck, et al. on Sept. 19, 1978.
While dot matrix printers were first designed to print in only a single color, more recently a color print capability has been added. A typical example of a color printer is disclosed in U.S. Pat. No. 4,289,069, entitled, "Method For Producing A Multiple Color Hard Copy Image", which issued to R. F. Melissa, et al. on Sept. 15, 1981. There a system is described which includes an ink ribbon having multiple zones of different colors carrying encoded identifying indicia. In response to input data defining a dot pattern in the color in which it is to be printed, the ribbon is searched to position the first identified ribbon color zone in front of the impact hammers. Two sets of coding holes for identifying the various colored zones of the ink ribbon are included on the edge of the ribbon which permits the ribbon to be inverted on demand as required; however, only one edge set of holes is used at a time.
Other color ribbon detection schemes are disclosed in: Japanese Pat. No. 55-154193, entitled, "Printer Adopting Multi-Color Ribbon"; Japanese Pat. No. 57-6786, entitled, "Multi-Color Ink Ribbon"; and Japanese Pat. No. 58-193184, entitled, "Thermo-Sensitive Color Transfer Apparatus". In the first mentioned Japanese patent, the color detection is provided by intervening zones of ribbon material containing color coded hole patterns. In the second Japanese patent, successive regions of multi-color ribbon are detected directly by light reflected from the surface of the ribbon. In the last remaining patent, a set of color code marks are included on the upper edge of the color ribbon having three primary colors alternating in sequence along the length of the ribbon.
Still another method of directly detecting different color segments of a print ribbon is disclosed in IBM Technical Disclosure Bulletin, Volume 22, No. 7, December, 1979, at pages 2633-2635 and being entitled, "Multi-Color Printing" by G. N. Baker, et al.
Accordingly, it is an object of the present invention to provide an improvement in impact type dot matrix printers.
It is a further object of the invention to provide a dot matrix printer for printing in a plurality of colors.
Another object of the invention is to provide a relatively low cost yet rugged color printer.
Still another object of the invention is to provide improvement in means for sensing different color segments of an ink ribbon utilized in connection with the impact type printer and thereafter selectively positioning a desired color segment in front of a print head.